Method and apparatus for treating moisture-containing substances



Nov. 24, 1936.. J. HARRINGTON METHOD AND APPARATUS FOR TREATING MOISTURECONTAINING SUBSTANCES 9 Sheets-Sheet 1 Filed Dec. 19, I931 JnmuvaGui/vase Cnnnasms Dawning-5p JL 0065 s N A F Z M i M f ,F. 7% m e M 9 0w J. HARRINGTON Nov. 24, 1936.

METHOD AND APPARATUS FOR TREATING MOISTURE CONTAINING SUBSTANCES FiledDec. 19, 1951 '9 Sheets-Sheet 2 Nov. 24, 1936. J. HARRINGTON METHOD ANDAPPARATUS FOR TREATING MOISTURE CONTAINING SUBSTANCES Filed Dec. 19,1931 9 Sheets-Sheet 3 Nov. 24, 1936. J. HARRINGTON METHOD AND APPARATUSFOR TREATING MOISTURE CONTAINING SUBSTANCES Filed Dec.- 19, 1931 9Sheets-Sheet 4 Nov. 24, 1936. J. HARRINGTON METHOD AND APPARATUS FORTREATING MOISTURE CONTAINING SUBSTANCES Filed Dec. 19, 1951 9Sheets-Sheet 5' Nov. 24, 1936. J. HARRINGTON 2 2 METHOD AND APPARATUSFOR TREATING MOISTURE CONTAINING SUBSTANCES Filed Dec. 19, 1931 9Shets-Sheet e 7 Nov. 24, 1936.

J. HARRINGTON METHOD AND APPARATUS FOR TREATING MOISTURE CONTAININGSUBSTANCES 9 Shets-Sheet 7 Filed Dec. 19, 1931 Nov. 24, 1936. J.HARRINGTON 2,062,025

METHOD AND APPARATUS FOR TREATING MOISTURE CONTAINING SUBSTANCESFiled'Dec. 19, 1951 9 Sheets-Sheet 8 Nov. 24, 1936. J. HARRINGTON METHODAND APPARATUS FOR TREATING MOISTURE CONTAINING SUBSTANCES Filed Dec. 19,1931 9 Sheets-Sheet 9 Nah V at x585. w bq 9x53 kwn I c Silk;

Patented Nov. 24, 1936 UNITED STATES PATENT OFFICE METHOD AND APPARATUSFOR TREATING MOISTURE-CONTAINING SUBSTANCES Joseph Harrington,Riverside, Ill. Application December 19, 1931, Serial No. 582,098

8 Claims. (01. 110-15) One of the objects of my invention is to pro videa process and apparatus for the economical and sanitary disposal ofsewage, including raw 15 sewage;

Another object of my invention resides in the provision of a process andapparatus for the economical and sanitary disposal of fluid sewagesludge by burning a mixture of sewage sludge m and fuel, preferably coalor coke, whereby to consume the sludge and/or create suflicient heat ofcombustion which can be utilized in drying additional quantities ofsewage.

Yet another object of my invention resides in theprovision of animproved process and. apparatus for the disposal of sewage comprisingthe addition of combustibly dry sewage sludge to burning fuel in amanner to prevent the fluxing of the two combustible ingredients, andwhereby 3 to provide sufflcient heat of combustion to dry additionalquantities of sewage to combustibly dry state.

Yet another object of my invention resides in the provision of a methodand apparatus for the 5 commercial and sanitary disposal of sewagewherein a bed or layer of sewage sludge is maintained in a substantiallyquiescent state while heated aeriform fluid is projected therethrough toreduce the same to combustible dryness.

40 Yet another object of my invention resides in the provision of aprocess and apparatus for the commercial, sanitary disposal of sewagecomprising forming a bed or layer of the sewage and simultaneouslyprojecting aeriform fluid through 45 the sewage and across the face of'the sewage to reduce the same to combustible dryness.

Still another object of my invention resides in the provision of aprocess and apparatus for the disposal of sewage which comprises forcing50 heated aeriform fluid through the sewage when projected in relativelyfine form whereby to reduce the same to combustible dryness.

Yet another object of my invention resides in the provision of a processand apparatus of the 55 above character comprising projecting heatedaeriform fluid through the sewage with suflici'ent velocity to cause thesewage to be projected in sprayed or relatively fine form whilesubjected to the action of heated aeriformfluid whereby to reduce thesewage to combustible dryness. 5 Yet another object of my inventionresides in the provision of a method and apparatus for disposal ofsewage comprising projecting heated air throughsewage with suflicientforce to cause a spray or projection of the sewage in substantially fineform while passing heated aeriform fluid and preferably heated gases ofcombustion through the sprayed sewage whereby to reduce the same tocombustible dryness.

Yet another object of my invention resides in 16 the provision of aprocess and-apparatus comprising projecting heated gases ofcombustionthrough the sewage withsuflicient force to cause the projection of thesewage in relatively fine form while at the same time passing heated ugases of combustion throughthe projected sewage and into contact withthe bed of the sewage to reduce it to combustible dryness.

.Yet another object of my invention resides in the provision of aprocess and apparatus for the commercial disposition of sewage whichconsists in the compact arrangement of a furnace for burning fuel and/orcombustibly dried sludge residue and in passing the products ofcombustion directly to a drier into which the sludge to be reduced isintroduced and/or in utilizing the gases of combustion for drying sewageeither by heating air for projection through and onto the sewage and/orby using the gases of combustion for projection onto and through thesewage, or by a combination of heated air and gases of combustionprojected through and onto the sewage, I

Yet another object of my invention resides in an improved process andapparatus for the sanitary and commercial disposition of substantiallyraw sewage by removing preliminarily a substantial proportion of thewater content of the sewage either by settling and/or filtering and/orevaporation and thereafter heating the partly de-watered sludge in amanner to eliminate the odoriferous gases and to reduce the sametocombustible dryness, and preferably thereafter burning the combustiblydried sludge residue and in utilizing the heat of combustion with orwithout added fuel for generating sufficient heat to carry out theevaporation and/or drying processes of further quantities of sewage.

Yet another object of my invention comprises the provision of animproved process and apparatus for the disposition of substantially rawsewage comprising partly de-watering the sewage by settling, activatingthe eilluent, recovering the partly de-watered sludge, and mixing thesame with the activated sludge and thereafter partly de-watering themixed fluid sludge preferably by preliminary evaporation or reduce it tocombustible dryness and burning the dried sludge residue whereby todispose of the sewage. 1 v

Yet another object of my invention resides in the provision of a processand apparatus for the sanitary and commercial disposition of sewagewhich comprises partly de-watering the sewage, thereafter ,heatingthesludge to reduce it to combustible dryness, and burning the sludge withadditional fuel whereby to dispose of the sludge and whereby to providesuflicient heat of combustion to reduce 'furthersewage to combustibledryness.

Yet another object of my invention resides in the process and apparatusfor the sanitary and commercial dispositon of sewage comprising thepreliminary evaporation by heat of substantially fluid sludge whereby torender the sludge substantially viscous to permit it to be continuouslyflowed in the form of a bed or layer, or tobe projected in finelydivided condition, and aubiected to heated aeriform fluid and reduced tocombustible dryness, and thereafter burned,

preferably in the presence of added fuel, to generate sufllcient heat ofcombustion to continue the heating operation for additional sewage.

Yet another object of my invention resides in the process and apparatusfor the sanitary and commercial disposal of sewage which comprisesburning combustibly dried sewage sludge with sufllcient fuel to generatesuflicient heat of combustion whereby to preliminarily partly evaporatesewage whereby to partly de-water the same and thereafter utilize theremaining heat of combustion in reducing the partly de-watered sludge tocombustible dryness by means" of the gases of combustion and/or byheated aeriform fluid including heated air and/or the heated gases ofcombustion.

Yet another object of my invention resides in the provision of a.process and apparatus for carrying out the process of the foregoingparagraph wherein the gases of combustion of'the burning sludge and/orfuel are utilized for preliminarily evaporating the sewage and forpreliminarily heating air to be used in the stoker or furnace and/or inreducing the sludge to combustible dryness.

Yet another object of my invention resides in the provision of a processand apparatus for disposing of sewage by reducing the same tocombustible dryness and burning which comprises utilizing the heat ofthe heating medium after said medium has so dried the sludge, forheating air to be passed to a furnace or other heating means and/or forheating air to be used in the drying operation.

Yet another object of my invention resides in the provision of a processand apparatus for the sanitary and commercial disposal of sewage sludgeby heating the same to combustible dryness and burning, which includesthe utilization of the heat of combustion and/or the heat from thedrying operation, for carrying out certain preliminary heatingoperations in the general process.

Yet another object of my invention resides in the provision" of aprocess and apparatus for drying liquid end/or fluid sludge to thecombustibly dry state by introducing the same when in finely dividedcondition into a maintained relatively high vacuum, whereby to quicklyevaporate the moisturecontent of the sludge.

Yet another object of invention resides in the provision of a processand apparatus for the reduction of sludge of substantiallyyeastcake-like consistency by finely dividing the same and projectingthe sludge through a highly heated aeriform fluid whereby to reduce thesludge to combustible dryness very quickly. 1

Yet another object of my invention resides in the provision of a meansand method for burning sludge containing less than substantially 25%moisture whereby to dispose of the sludge and to eliminate odoriferousgases.

These and other objects of my invention will be apparent from a perusalof the following speciilcation taken in connection with the drawings,wherein Fig. 1 is a diagrammatic flowsheet showing the flow of the air,sludge, hot gases and steam tothe various elements of the system;

Fig. 2 is a building arrangement and side elevation showing the variouselements of the system in relation to one another, the preliminary;

treatment of the sludge not being shown in the figure;

Fig. 3 is a plan section view of the complete arrangement shown in Fig.2;

Fig. 4 is a cross section taken on line 4-4 of Fig. 6 shows stillanother arrangement for eco-.

gomically carrying out the process of my inven- Fig. '7 is a detailedplan view of one type of furnace that I may use in connection with theapparatus shown in Figs. 2, 3, and 4;

Fig. 8 is a cross section of the furnace and evaporator taken on line8-4 of Fig.- 'I;

Fig. 9 is a side view of the type of drier shown in connection with theapparatus illustrated in Figs. 2, 3, and 4;

Fig.- 10 is an enlarged detailed view of thedrier shown in Fig. 9;

Fig. 11 is a partial plan view of the drier shown .in Figs. 9 and 10;.

Fig. 13 shows an arrangement of float control for feeding the sludge tothe drier;

Fig. 14 is a perspective view showing the formation of the sludge bedwhen subjected to the action of the heated aeriform fluid;

Fig. 15 is a detailed perspective view of the means for deflecting theheated aeriform fluid to the underside of the drier;

My invention is applicable to the sanitary and commercial disposition ofsewage having various percentages of moisture content. In certainaspects it is adaptable to the disposal of sewage containing as high as99 /2% water content, 1. e., raw. or substantially raw sewage. Incertain other aspects the invention is applicable to the disposition ofsewage sludge containing substantially as low as 70% moisture content.The process and apparatus are adaptable to the sanitary and commercialdisposition of sewage in liquid, or fluid, condition.

For purposes of illustration I have disclosed one form of my inventionas applicable to the treatment and the disposal of raw sewage, whichcontains substantially 99 moisture content, including the manner inwhich the efliuent from the settling chambers and sedimentation tanksused in the process, is conveyed to the activated sludge tanks and themanner in'which the activated sludge is connected into my process orsystem for its sanitary disposal along with the partly de-watered sludgecoming from the sedimentation tank. My invention is equally applicableto sewage containing less moisture content, it being obvious that theexact details of the process and apparatus which is herein showndiagrammatically is subject to many modifications and changes inaccordance with the type of sludge or sewage to be treated, with localconditions, and other factors which might cause variations of thegeneral principles of my process and apparatus.

In order to exemplify the general principles of one aspect of myinvention for the treatment and/or destruction of sewage in a sanitaryand commercial way, I shall now describe the complete process andapparatus for the treatment of raw sewage as is shown in thediagrammatic the other heavier suspended matter to the bottom to bedrawn off continually with about 15% of the average flow and passed tothe grit chamber. These skimming tanks are provided with mechanicalequipment for removing the bottom sludge and the top surface scum. Fromthe skimming tank the top flow or eflluent, which amounts to arelatively large proportion of the contained water, may be run, asillustrated at 8, to the activated sludge tank if desired. The bottomflow of the somewhat thickened sludge from the skimming tank is passedby means of pipe ID to the grit chambers l2 where the velocity isgreatly decreased and where the heavy gritty material suspended in thesludge settles to the bottom and from which place it is periodicallyremoved. At the discharge from the grit chambers the sewage issubstantially in its original condition except for the removal of coarsefloating particles, heavy sand and other mineral substances, and aportion of the water. From the grit chambers the sludge flows to asedimentation tank I 4 where the sludge is detained for suflicient timeso that the stuff may settle quite rapidly. The clear effluent may bepiped from the top, as at l6, and conducted to the activated sludgetanks. The heavy stuff which is considerably thickenedsludge, is run-01ffrom the bottom of the sedimentation tank by means of pipe It. Thissludge thus partly de -watered, contains about 96% moisture and is inthe form of a relatively thin liquid. Preferably, but optionally, theactivated sludge from the activated sludge tank 22 may be piped as at 24into-the conduit that conducts the partly de-watered sludge to theremainder of the apparatus and the clear eflluent flowing through pipe26 in the activated sludge tank may be conducted to the river or anyother desired point.

The various steps in the process for preparing the sewage sludge fordestruction by heating and burning may be subjected to many alterationsand changes. For instance, the steps shown in the flow sheetof Fig. 1including the coarse screening, preliminary settling chamber, and gritchamber and sedimentation tank treatment may be re-arranged and alteredand other process and apparatus substituted in order to provide suitableliquid conditioning features so as to prepare thesewage for thesubsequent heating and burning. These variations and changes will begoverned by the type of sewage used, factors of economy and localconditions.

In the arrangement shown, the partly dewatered sludge with the activatedsludge added thereto, in liquid condition, may be pumped by means ofpump '48 through pipe 30, through a preliminary heat' exchanger32'-'==.where the raw sewage at approximately 50 degrees Fahrenheit,assuming that temperature to be the average temperature of the sewagethe yearj'iround, can be raised to about to 200' degrees Fahrenheit. Iprefer to use this heater because I can utilize some of the heat fromanother part of the process prior to its final discharge up the stack.

From the preliminary heater 32 the fluid sludge at approximately 96%moisture content is preferably passed through a sludge concentrator andevaporator. By so doing, I am enabled to utilize heat from some otherpart of my process and apparatus which would otherwise escape to theatmosphere, for the purpose of concentrating the sludge or preliminarilyreducing its moisture content whereby the heating to be done in the maindrying operation is less and whereby the substantially liquid sludge maybe preliminarily conditioned or changed to a substantially viscous statefor the particular type of drying operation carried out in the dryingmechanism. That is to say, where I dry the sludge byforming it in a bedor layer on a foraminated or porous support and project heated aeriformfluid therethrough, the viscous sludge is in better condition to remainsupported on the porous support than would be sludge having a muchgreater water content. In addition to the above advantages, there isanother benefit derived in connection with the process, wherein heatedair, as distinguished from hot gases of combustion is utilized in wholeor in part as a medium for drying the sludge in the'drier. In such acase, the air must be passed through some type of heat exchanger whereit is heated by hot gases of combustion and I have found that it isimpractical to pass hot gases having a temperature of 2500 degreesFahrenheit or thereabouts through a heat exchanger, and therefore bypassing the hot gases of combustion at such high temperature firstthrough the preliminary evaporator for concentrating the sludge, I amenabled at the same time to reduce the temperature of these hot gases sothat they can be utilized in a heat exchanger for heating the air in themanner described.

Inthisevaporator,from50%to00% cspcasibiy more of the total moisture isremoved from the sludge. bearing in mind that the sludge in theevaporator must remain in a state of fluidity in order to be circulatedthrough the evaporator in the manner hereinafter described. In certaininstances with certain types of sludge, it is possible to evaporatesubstantially as high as 80% of the moisture content in this preliminaryevaporator and still have the sludge remain fluid in I passes by meansofpipe 38 to the drier which I prefer to associate with a furnace in sucha map ner that the sludge, when reduced to acrimbustibly dry state, ispassed to the furnace and with the addition of sufficient quantity offuel, burned in the furnace. The heat of gases of combustion is thenutilized in turn, in a continuous manner, for drying further quantitiesof the sludge.

In connection with certain aspects of my invention, in this sludgedrying operation I may use any type of heated aeriform fluid includingthe direct utilization of the gases of combustion and also includingheated air and/or both. In the present specification, the term heatedaeriform fluid is used to express any type of heated aeriform medium fordrying the sludge to combustible dryness. To make clear my references tosludge of combustible dryness, it should be said that the use of thisterm implies a, state of dryness wherein the combustible portion of thematerial will burn freely, generate a hot fire and provide enough excessheat for use in other parts of the process, or in performing operationsother than the burning of the sludge itself; While this is not a fixedfigure, I assume that a moisture content of 25% or less renders thesludge dry enough to burn and provide heat for other purposes as abovedescribed. It will be understood, of course, that sludge having amoisture content ranging from substantially 25% to substantially 50% canbe burned without the addition of fuel thereto so as to consume anddispose of the sludge. How ever, in those instances where I desire toutilize the heat of combustion for drying additional quantities ofsludge to combustible dryness, it is necessary to add additional fuel tothe sludge. While I prefer to add this fuel in the furnace in the mannerdisclosed, it may be added at any desired point in the process.

Referring to Fig. l, and describing the apparatus and process in generalterms, the sludge forced through pipe 38 is fed into the hopper of thedrier and thence is formed in a bed or layer of viscous sludge in thedrier in a continuous manner. The bed so formed preferably continuouslymoves while the heated air is projected continuously through pipes 42,44, 46 and 48, through the bed whereby to reduce the'sludge tocombustible dryness. The heated air, after passing through the sludge,together with the evaporation products of the bed'are caught in a hood50 and conveyed by means of a'pipe 52, and are thence passed through afirst stage heater or heat into pipe 00. Y

Simultaneously and therewith the 'combustibly dry sludge is depositedfrom the drier onto a conveyor ill and fed to afurnace I. The driedsludge, together with sumcient fuel, either oil, coke, coal, or anyother type of fuel may be burning of the sludge, and also that theproducts of combustion may be utilized in carrying out the drying ofcontinuous quantities of sludge, and/or the preliminary evaporation of aportion of the moisture content of the fluid sludge whereby the dryingoperation may be rendered more economical and expeditious, and thesludge beconditioned for more facile handling in the drier. Also, insome instances, so that the hot gases of .combustion coming from thefurnace may have at least a portion of the heat thereof removedpermitting the gases to be put through a heat exchanger for heatingvolumes of relatively cold air utilized subsequently in the dryingoperation.

The hot gases of combustion created in the furnace by the burning of thefuel and combustibly dry sludge are passed through the evaporator andthence are passed through a second heater or heat exchanger 62, fromwhence they emerge through pipe 64, and are thence passed by a suitablefan or blower 66 by pipe 68 to the stack 10; The heat exchangers 54 and02 are provided with suitable passages through which air may flow to thefurnace and to the drier mechanism. For instance, air may be conveyed bymeans of pipe 12 and will pass in divergent paths to pipes 14 and [6through the first heat exchanger where the temperature of the air willbe raised sufliciently. The pipe 14 will connect with the furnacewhereby heated air maybe utilized in the furnace for burning the fueland sludge. The heated air passing through pipe 16 will then pass in aseries of relatively small pipes 18 through the second heat exchanger orheater 62, where the air passing therethrough will have its' temperatureraised substantially. If desired, each pipe 18 conducting the air mayhave a separate fan driven by a separately controlled electric motor,for the purpose of governing the volume and pressure of the heated air,and in addition, any suitable controlling means may be utilized forvarying the temperature of the air which passes through the pipes 42 to48, whereby to control the heat within and longitudinally of the drier.In certain instances I prefer to provide the pipes 46 and 48 carryingthe heated air from the pipes I8 and which pipes 46 and 48 project theheated air into the endmost sections of the drier, with means fordiluting the heated air passing therethrough with suitable andcontrolled quantities of cool air in order to prevent overheating of thesludge at the end of the drier. For this purpose I provide an additionalair pipe 80 provided with a blower 82 and which pipe 00 connects withpipes 46 and 48 and is provided with suitable air valves 84 and 86 whichmay be adjusted to cause suitable dilution of the air.

During the evaporation of the fluid sludge in the evaporator itrelatively large volumes of steam and vapor products are given off whichare conveyed by means of pipes 88 through the heat exchanger 32 so thatthe heat from the steam may be utilized for preliminarily warming thesludge passing through the heat exchanger".

This steam, after passing through the heat exchanger 32 is preferablyconducted through the first heat exchanger 54 for the purpose "of stillfurther utilizing the heat thereof. I may join the pipe 08 with the pipe52 through which the heated air and vapor products from the drier arebeing conducted and to pass the same in mixed condition through thefirst heat exchanger 54. The hot gases and steam discharged through pipe56 are put thrbugh an obnoxious vapor condenser andv are thence forcedby a fancr blower 92 through the stack 10.

Instead of combining the steam which is derived from the evaporation ofthe sludge in the concentrator with the steam collected from above thedrier, I prefer to divert the steam from the evaporator to otherpurposes, such as radiation for heating the building, or any otherprocess which may be associated with this apparatus requiring heat. Itshould be noted that the amount of heat recoverable from the steamarising from the drying sludge on the drier is sufficient for heatingpurposes desired in the preliminary heater.

Thermal aspects of process.

I shall select the process shown in Figs. 1 to 4 of the drawings as anillustration for exemplifying the thermal aspects of my invention asapplied to treatment and destruction of sewage sludge as it is deliveredto the preliminary heater with a moisture content of substantially 96%.Referring again to Fig. 1 of the drawings, as the sludge passes throughthe first heater 32, it is warmed from an average temperature of 50degrees Fahrenheit to approximately to 200 degrees Fahrenheit, and isthen passed to the concentratoror evaporator which latter is subjectedto the hot gases of combustion from the furnace having a temperature ofapproximately 2500 degrees Fahrenheit. In this evaporator, substantiallyfrom 50 to 60% of the moisture is removed from the sludge so that thedewatered sludge with approximately 90% moisture content or even lowerin certain instances, is passed through the drier. Simultaneouslytherewith, the gases of combustion which have concentrated the sludge inthe evaporator now pass to the first heat exchanger at a temperature ofsubstantially 1500 degrees Fahrenheit, where such gases are utilized forheating the air which is to be projected through the sludge bed in thedrier. The thickened sludge of approximately 90% moisture content isthen fed onto the drier which forms it as a relatively thick sludgeblanket of from three to six inches in thickness. As a result of theprojection of the heated air through the continuously forming and movingsludge blanket, the sludge is reduced to combustible dryness and in theparticular instance, the dried sludge contains from 10 to 15% ofmoisture. The heated air and vaporous products that are discharged fromthe drier and having a temperature of about 300 degrees Fahrenheit areconducted through the first heat exchanger so that the heat from thesedischarged gases will be ultimately recovered and preliminarily used forheating the air which not only passes through the furnace but also whichpasses through the second heat exchanger through which it will beremembered the hot gases of combustion from the furnace at 1500 degreesFahrenheit are passed. In addition, the steam generated in theconcentrator and evaporator by the preliminary evaporation of the sludgeis conducted at a temperature substantially 212 to 250 degreesFahrenheit through the sludge warmer to impart a preliminary rise intemperature to the sludge as hereinbefore described and may be conductedtogether with the hot air and vapor discharged from the drier, throughthe first heat exchanger as hereinbefore described. In in-. stanceswhere my process begins with the preliminary concentration orevaporation of sewage having a moisture content of substantially 96%,when such sludge is finally reduced to a combustibly dry state in themanner hereinbefore described, I burn this sludge in the proportion ofone part by weight of sludge and two parts by weight of fuel in thefurnace whereby to generate sufficient heat of combustion to carry on ina continuous manner the evaporation and drying operations hereinbeforedescribed. In addition, the heat of combustion generated within thefurnace is sufficiently hot, ordinarily, to destroy all odoriferousgases resulting from the burning of the dried sludge. It is thoughtpreferable, however, to provide a condenser for the obnoxious gases inorder to insure against the pollution of the atmosphere around the plantin the event that the apparatus is inexpertly or inefliciently handled.The proportions of fuel to be added to the combustibly dry sludge aredetermined by the moisture content of the sludge subjected to the dryingprocess.

It will thus be observed that by the utilization of my process includingthe utilization of the heat of the products of combustion in the furnacein preliminarily evaporating the sludge and in carrying out the mainsludge drying step and also in the utilization of the heat of dischargefrom the drier in the preliminary heating of the air which passes to thefurnace and through the second heat exchanger, and the utilization ofthe steam discharged from the evaporator in the manner described, andthe utilization of the combustibly dried sludge with added fuel forcreating the hot gases of combustion I provide a most economical,commercial and sanitary apparatus and method for the destruction ofsewage sludge.

Referring now to the details of construction of I By reference to Figs.2, 3, 4, 7, and 8, it will be seen that I have arranged the furnacepreferably at one end of the drying and burning apparatus,

which is preferably arranged within a building or structure having anoutside stack. The furnace, of desired construction, includes the usualmovable grate 98 onto which coal, coke, or other fuel, I00, may be fedby means of the hopper I02, in turn fed by a spout I04 from thereservoir I06, in turn fed by external conveyor I08 as desired. The hotair in pipe I4 from the first heat exchanger 54 is forced by means of ablower H0 in the usual manner through the movable grates. In addition tothe fuel inlet the furnace is also provided with other fuel inlets I I2disposed vertically above the fuel bed. These inlets I I2 are providedwith hoppers Ill which are fed by means of a conveyor H6. This conveyortransports the combustibly dried sludge which has been dried in thedrier 50 and feeds it in continuous measured amount to the hoppers Ill,

' ucts of combustion when necessary. This stackwhere the combustibly drysludge H3 is kept in agitated tondition by means of a suitable agitatorI20 driven by a belt I22 from a source of power. In addition, this samesource of power is provided with eccentrics I24 for reciprocatingfeeders I26 whereby to positively feed measured amounts of thecombustibly dried sludge to the feed channels I I2 where the sludge willdrop in a layer onto the burning fuel bed. By stratifying the driedsludge in a superimposed layer with respect to the burning coal or fuelbed, I am able to prevent the fluxing of these fuels. The burnt fuel andsludge will pass from the fuel bed into a suitable receptacle where ashcan be removed. Meanwhile the products of combustion at substantially2500 degrees Fahrenheit more or less will pass through the furnace gasdischarge I28 and across and about the vaporizing tubes of thepreliminary evaporator for removing a portion of the moisture content ofthe sludge prior' to its reaching the drier. The furnace is providedwith an emergency stack I30 for diverting the prodis temporarily closedby means of a gate I32 which may be opened when desired by any suitablemechanism.

Preliminary rte-watering of sludge In order to render my sludge dryingprocess more economical so that the sewage can be heated moreeffectively and quickly in the drier, I prefer to preliminarily partlyde-water the sewage prior to passing it to the drier. The de-wateringoperation can be carried out in any desired manner and with any desiredapparatus. In the present instance I have disclosed this preliminary,partial de-watering of the sewage to be carried out by means of partialevaporation by the application of heat for the purpose of reducing themoisture content of the sludge. However, it is to be understood that anydesired type of de-watering may be used including centrifuging of thosedevices shown in my pending application. Accordingly I pass the liquidor fluid sludge preferably first through the preliminary evaporatorbefore pass ing it to the drier mechanism. The preliminary evaporator isadapted to remove from substantially 50 to 80% of the moisture from thefluid sludge. I

In those instances where the main drying of the sludge is accomplishedby the drying process and apparatus shown in Figs. -1 to 4 of thedrawings, 1. e., where it is desirable to have the sludge maintained ina -s'u bstantially fluid conditionwhile heated aeriform fluid is" projected therethrough,

it is necessary that the sludge from'whlch substantially 80% of themoisture has been removed; be of such character that when so partly "dewatered, it is still substantially fluid. However, it is to beunderstood that my process and apparatus is not so limited and that myinvention.

includes the drying of any type of sludge which has been partlyde-watered, whether it be either in fluid or non-fluid condition. I g

In addition to reducing the moisture content of the sludge, thispreliminary sludge evaporation step is utilized in instances where Idesire to heat air by means of the products of combustion,

for accomplishing the drying of the sludge, and

in such instances, by passing the hot gases from the furnace which aresubstantially around 2500 degrees Fahrenheit, first through theevaporator, a considerable portion. of the heat of the gases isextracted in evaporating the fluid sludge, and the gases of combustionwith their temperature thus lowered, may then be utilized for passingthrough a suitable heated chamber or passing into contact with any typeof metallic surface without injuring or damaging the same. As a specificinstance, the hot gases at substantially 2500 degrees 5 Fahrenheit onpassing through the evaporator will evaporate a portion of the moisturefrom the sludge, and in doing so they will leave the evaporator atsubstantially 1500 degrees Fahrenheit. In this condition they aresufficiently low in tem- 4o perature to be passed through the heatexchanger 62 for heating the air on its way to the drier. The gases onpassing through the heated chamber will be discharged therefrom atsubstantially 400 degrees Fahrenheit and will be passed up the 15 stackat a comparatively harmless temperature. In the form illustrated inFigs. '1 and 8 of the drawings I have selected a well-known type of longtube evaporator and have arranged the sludge heating tubes thereofdirectly in the path of travel 20 of the products of combustion as theycome from the furnace. This particular type of evaporator which is ofwell-known construction embodies a lower header I34 which connects witha sludge pipe 34. This header I34 communicates with a plurality ofrelatively long tubes I38 which in turn discharge into a second headerI33 wherein are located a plurality of semi-circular deflectors I40which deflect the sludge outwardly so that it will fall down into thechannel I42 provided by the upstanding flange I 44. The formation ofsteam bubbles in the bottom ends of the long tube I38 causes a violentupheaval of the combined water and steam, like a geyser, which shootsthe sludge upwardly through the tubes and causes the sludge to impingeon the curved baifles within the upper drum, whereby the sludge isdeflected downwardly in the manner shown, and whereby the steam canescape laterally and upwardly. The sludge is pumped from the channel I42through the pipe 33. The steam and vapors from the evaporated moistureof the sludge passes out through the pipe 84. Any number of theseevaporators may be connected in a battery. In the present instance Ihave shown 45 three. It is obvious that I may use the two stageevaporator, in which case the sludge passes serially through both of thestages and the steam for the first stage is passed into the second stageas the heating medium. This type of'device willevaporatesubstanti'ally80% of: the moisture.

The form of dryingmechanism illustrated in detailin Figs. 9; .10, 11,12, and 13,.is substantially like that shown in my priorpendingapplication hereinbefore referred to; In general, it comprisesmeans: for forming a blanket orlayer or bedoffluid sludge preferablyabout four inches-in thick-' ness, but which thickness may be varied asde-l c0 sired, and preferably means for moving the bed of sludge whileat the same time projecting heated aeriform fluid into contact therewithand preferably therethrough. The bed ispreferably moved continuously,although it may be moved s5 intermittently, and I prefer to project theheated aeriform fluid upwardly through the bed and with suflicient forceto cause the fiuid sludge to bubble and spout whereby the fluid sludgeis projected or sprayed somewhatso that the globules and relatively finespray may be more quickly brought into contact with theheated aeriformfluid and the drying effect hastened. Except for the turbulent conditionof the sludge bed at that .portion thereof where the bed first receivesthe 7 force of the heated aeriform fluid therethrough, the sludge bed isotherwise maintained relatively quiescent, that is, it isnot disturbedby raking, working or by any other mechanical means. By referring toFig. 14 which represents, in a general way, the manner in which a bed offluid sludge is transformed progressively from the fluid or even viscousstate to complete dryness by the projected heated aeriform fluidtherethrough, it wfll be noted that when the previously prepared sludgecontaining a moisture content so that the sludge is still fluid, is fedonto the drier in the form of a blanket or bed, it is still suflicientlyliquid so that it will spread out into a layer of substantially uniformthickness by virtue of its own fluidity and will permit freely theupward passage of air bubbles. As the heated aeriform fluid is projectedtherethrough with suflicient force, the appearance of the surface of thesludge as it is first subjected to the aeration treatment is one ofviolent ebullition, as shown at I46, with steam bubbles emerging andbreaking at the surface of the liquid just the same as on the surface ofa pan of water. These geysers or sprays of fluid sludge includingglobules of sludge .will

be projected at times some distance from the bed of the sludge. As thedrying proceeds, the character of the sludge changes to more and moreviscous condition until toward the end of the period of fluidity, thesludge takes on the appearance of cornmeal mush in its later stages. Thebubbles of air and/or gas burst and leave voids, spaces or holes in thesludge bed, which closeup with ore or less slowness, depending upon theviscosity of the fluid, until finally the viscosity reaches such a stagethat these holes or voids caused by the passage of the heated aeriformfluid therethrough do not close but remain open and thereby formpermanent channels or spaces through the then solidified sludge. As theheated aeriform fluid is continuously projected through the drying bedof sludge, these permanently formed holes permit large quantities ofheated aeriformfluid to pass through the layer of drying sludge in sucha manner as to readily facilitate the carrying off of the moisture andthe reduction of the sludge to combustible dryness, i. e., to areduction of the moisture content to less than substantially 25%. Themanner of progressively drying the sludge including the automaticformation of air holes through which the heated aeriform fluid may beprojected eliminates the necessity of providing some mechanical meansfor puncturing, breaking up or rendering the sludge bed porous to permitthe heated aeriform fluid to pass therethrough.

As long as there is moisture to be evaporated, and as long as the heatedaeriform fluid actually passes through the fluid sludge, there will be avery rapid interchange of heat from the heated aeriform fluid to thefluid sludge, causing actual steaming or vaporization of the moistureand loading the air or gases medium itself with as much moisture as thatheated aeriform medium at such temperature can carry. As the dryiprocess proceeds, however, and the aforementioned holes in the sludgebed become permanent, considerable quantities of air can pass throughthese holes without direct contact with the moist material and due tothe lack of fluidity at this stage in the process, it is possible to dryone portion of the stifl mud-like sludge while the other portionsthereof are still actually wet. Under these conditions it is possible toactually dry and ignite the edges of a piece of sludge,

or those portions at the periphery of the above mentioned holes whilestill retaining wet por- Inasmuch as it is not.-

tions between the holes. desirable to have the sludge partly burnt orcharred at this state of the process I have found it desirable toprovide means for lowering the temperature of the heated aeriform fluidtoward the end of the drying process to such a degree as to prevent theoverheating of portions of the sludge, and also, owing to the reductionin the resistance to the passage of air, by the porosity abovedescribed, I find it also desirable to reduce the pressure of the heatedaeriform fluid at this portion of the drier.

Referring now to the mechanical details. of the drier construction forcarrying out one process for drying the sludge, the drier comprises twosprockets I48 around which passes the endless link chain I50 of anydesirable construction, and which links at their pivotalinterconnections carry rollers I52 adapted to roll along a horizontalguide-way I54 whereby to keep the supporting bed of the sludge in leveland in uniform condition. In addition, each of the links between itspivotal connection carries a cross bar I56 which is supported from anupstanding arm I58 carried by the link, and in turn, each cross barcarries a series of spaced-apart sludge supporting elements, preferablyin the form of longitudinally extending relatively narrow bars I60,which are supported on the bars I56 preferably at their centralportions. Each of these bars extends on opposite,sides of its centrallyarranged supporting bar I56 a distance substantially equal to thecentral portion of the next supporting bar I56, there being a space leftbetween the ends of two adjacent bars so as to permit the bars to turnabout the end sprockets in the manner shown in Fig. 10. By arranging thebars in staggered overlapping relation in the manner shown in Fig. 11,the bars provide a sludge-supporting surface formed with a multitude ofvery small openings or spaces therebetween. For one type of sludge, inthe present instance, these openings or spaces between the bars arepreferably substantially 1/40th of an inch in width. The bars in crosssection shown in Fig. 12 taper in a downward direction so as to providesuflicient clearance for any sludge that may pass therethrough wherebyto prevent clogging. The construction of these bars is disclosed andclaimed in my prior mentioned application, and it is understood thatthese bars extend across the entire width of the carrier betweenthelinks so as to provide a bed of considerable width. Only a part of thebed is shown.

The under surfaceof the upper portion of the drier and over which thesludge supporting mechanism passes, is dividedinto a number of chambers,preferably four, which are separated by partitions I62 arranged so as topreserve contact with the lower edge of the uprights I58 which supportthe cross-bars I56. These partitions I62 are provided with suitableinterior facings of insulation I 64, and are also provided withlongitudinally extending sheet metal wall members I66 having outwardlyextending looped portions I68 which resiliently press against the innerfaces of the supports for the cross bars I56 so that as these cross barspass over the stationary partition I62, a resilient wiping effectbetween the resilient fingers I68 and the traveling support for thecross members I 56 will ,prevent the escape of the heated aeriform fluidat the junction of the traveling sludge-supporting bed and thestationary chamber forming member. In addition, each cross bar I56 andits support is provided with an upstanding partition member I16preferably of sheet metal. These partitions are provided withoutwardly'extending tips I12 adapted resiliently to overly the adjacentends I14 of similar partitions carried by the next adjacent cross barI56 so that when the cross bars and their sludge carrying platforms arepassing along the horizontal frame of the drier, that is when theendless belt carrying the members I66 is passing along during the dryingperiod, these upstanding plates I16 will form a closed side for thedrier above the drying bed. In addition, the upper ends of these platesI16 will resiliently contact with a spring metal finger I16 carried bythe depending edge of the hood 56 which overlies the drying chamber. Thearrangement of the side wall members I16 in overlapping relation asshown in Fig. 11 permits these plates I16 to separate when they passaround the sprocket I46. As an additional means for closing in andsealing each one of the chambers or compartments into which the heatedaeriform fluid is projected, I provide each one of the cross supportsI56 on its under side with a closure of preferably resilient sheet metalwhich has one end afllxed in any suitable manner to the dependingportions I16 of the cross bar I56. This sheet metal sealing memberextends under and rearwardly of the bar I56 and is adapted to wipe overa. guiding member I66 mounted on the top of the cross wall of eachpartition I64 and I 62. By means of the resiliency of the trailing edgeI62 and its wiping action along the upper surface of the member I66 thesealing eflfect of each compartment is assured. It will be understood,of course, that these sealing members I62 extend entirely across thewidth of the chambers I64 and thus prevent aeriform fluid, which isforced into each chamher, from passing into the other chamber. Inaddition to the aforementioned details, the hood 56 opposite eachchamber is provided with an observation window I64 for the purpose. ofwatching the progress of the sludge drying operation at the variouscompartments forming the different stages of drying.

Itwill be understood in the preferred embodiment the endless belt andthe sludge supporting member are moved in a continuous manner by anappropriate means. And in order continuously to form a bed, blanket orlayer of fluid sludge of substantially uniform thickness in an automaticmanner on the upper surfaces, of the bed supporting members I66. anysuitable means may be utilized. In the present instance I have shown oneembodiment of a suitable .means comprising a box-like device I66extending the width of the drier surface with its discharge end locatedbetween the side partitions I16 and disposed over the receiving end ofthe sludge supporting elements I66 and in a position so that as thesemembers are formed in closed relation and moved forwardly the fluidsludge will flow through the discharge gate I66 over a flexibledistributing tongue I66 preferably of heat-resisting material wherebythe sludge will be formed in a layer of desired thickness. In thepresent instance,,a bed of sludge of uniform thickness approaching fromtwo to six inches in depth may be provided. Means is provided forcontrolling the flow of the sludge into the chamber I66. In the presentinstance, this comprises a float I62 operated by the level of the fluidsludge in the box I66 and adapted to operate a valve I64 in'a pipe I66through which the sludge flows from the pipe 66 coming fromtheevaporator as hereinbefore described.

It will be understood. of course, that the sludge supporting barsproviding a porous or foraminated surface through which heated aeriformfluid is adapted to be forced may be constructed in anydesirable mannerin accordance with the teachings of my hereinbefore described pendingapplication.

Means is provided for supplying the chambers formed in the partitionsI64 with heated 'aerifoi'm fluid for projection through the sludge bed.One manner of accomplishing this is shown at Fig. 15 of the drawingswherein the details of construction of one of the manifolds I66 is.shown. Each one of these manifolds is provided with an inlet bus pipe266 through which heated aeriform fluid is adapted to be forced. Theinterior portion of each manifold is provided with a plurality ofdeflecting members 262 arranged to distribute the heated aeriform fluidand to deflect it upwardly through the interstices between the sludgesupporting bars. I

Referring now to Figs. 2, 3, and 4 of the drawings wherein is disclosedthe apparatus the details of which form the subject matter of Figs. 7,8, 9, 16, 11, 12, 13 to 15 of the drawings, and wherein the various airpipes interconnecting therewith as shown in the flow sheet of Fig. 1, itwill be appreciated that in the compact arrangement of the variousfeatures forming my apparatus or system, the relatively large structure264 is adapted to house or enclose these various features and that thearrangement is such that the stack 16 is preferably disposed outside ofthe housing. With reference to Figs. 2, 3, and 4,'

it will be seen that the furnace 66 shown at the left of the figure andprovided with emergency stack I66 receives its fuel from the hopper I62and is passed through heat exchanger 54, thence through pipe 16, blower16, thence through pipes 42 to 46 into the four separate chambers of thedrier'from which point the heated air is'projected through the sludgebed. At the same time the heated aeriform fluid which includes theheated air and vapor products are captured by the hood 56 and passedthrough pipe 52 from which point these gases are carried over and passedthrough the flrst heat exchanger 54. Simultaneously therewith the steamand water vapors from the evaporator 36 are passed through steam pipe 66through the sludge warmer 62and thence are injected by means of the pipe66 into the pipe 52 through which the hot air is passed to the firstheat exchanger 54. The hot air and water vapor is discharged from theheat exchanger 54 through the pipe 56 through the obnoxious vaporcondenser 66 and thence is passed by means of a suitable blower up thestack.

The fluid sludge is pumped by means of pipe 66 through the preliminarysludge warmer 62 66 to the float control box I66 at the receivingaocaoas or front end of the drier. After the sludge is dried, it isdischarged from the end of the traveling drier into screw conveyor 66from which point it is fed into the hopper Ill which feeds into thefurnace.

In certain instances quicker drying and more economical operation can becarried out by simultaneously projecting heated aeriform fluid throughthe sludge bed while also passing heated aeriform fluid over and acrossthe face of the sludge bed. In this type of process and apparatus, theforce of the heated aeriiorm fluid which is projected through the sludgebed, as before described, will project the substantially fluid sludgeupwardly-in a spray or flnely divided condition for a suflicient heightso that heated aeriform fluid can at the same time be passed through andacross this projected sludge and across the face of the bed for thepurpose of more quickly drying the sludge. In this type of apparatus theheated aeriform fluid may consist of air and/or hot gases of combustionor the hot gases themselves may be utilized directly.

In Fig. 5 of the drawings I have shown an apparatus for \carrying outjust such a process. In this figure thefurnace 66 with its emergencystack I30 is arranged to burn the combustibly dried sludgefed into thehopper H4 and the furnace gases, i. e., the hot gases of combustion, arethen passed from the furnace directly into contact with the sludgeconcentrator and preheater 36 just as in the process and apparatus asshown in Fig. 2. After passing through the sludge concentrator, the hotgases of combustion pass through a relatively long tunnel-like conduitwhich is arranged immediately above the drier oi the form shown in Fig.2. In Fig. 5 the drier is provided with the usual compartments andprovided with means for projecting heated air through the compartmentsas in the manner described in Fig. 2, however, in Fig. 5 the roof of thedrier comprises preferably a metallic plate 266, preferably ribbedheavily on its inside and designed to absorb the heat of the gases andtransfer said heat to the air passing through the conduit 2H! formedbetween the plate 208 and the insulated casing member 2l2 forming a partof the heat exchanger. This heat exchanger is disposed above the drierand is arranged so that air going through pipe 2 is passed through theheat exchanger and into conduit 2 l while at the same time the heatedgases of combustion will pass through the heat exhanger in a manner wellknown in the art and isolated from the incoming air so as to cause aheating of the air to a relatively high temperature in the mannersomewhat after that shown in the apparatus of Fig.2. In the constructionshown in Fig. the hot products of combustion after passing through theheat exchanger are passed through an obnoxious vapor condenser 2|6 andthen conducted through conduit 2" by a blower 226 to the stack 222. Asuitable liquid condenser 224 is inserted in the line for carrying oficondensed water and other liquid. The heated air passing through theconduit 2) above the drier is extracted by means of suitable blowers 226through the ports 228 and forced into the four separate chambers ofthedrier from which point the heated air is projected through the sludgebed in the manner described in connection with Fig. 2 of the drawings.The heated air being forced up through the sludge bed at high velocitiescauses the fluid sludge on the drier violently to boil and to throw aspray up into the air a sumcient height so that the products ofcombustion going through the tunnel-like conduit immediately above thesludge bed will pass among the globules or spray of sludge and cause thesame to be rapidly dried in a very simple manner. In Fig. 5 of thedrawings, the course of flow of the products or com-- bustion isindicated by the heavy dash and dotgrammatically in Fig. 6, instead ofusing heated air for projection through the sludge bed, I utilizedirectly the gases of combustion forcing them not only through thesludge bed in a manner therewith project these hot gases of combustionthrough the ebullient sludge bed and there across while at the same timeextracting 'sufiiclent amounts of these gases of combustion and passthem through a separator for removing ash and other undesirable foreignmatter in the gases of combustion and thence return these hot gasesdirectly through the bed of sludge. In this figure likewise the path offlow of the hot gases of combustion is indicated as taking the coursefrom the furnace 66 through the sludge concentrator 36 thence through asubstantially tunnel- 'hereinbeiore' described, but -I simultaneouslylike conduit 230 formed by an insulatingroof over the drier. Theseproducts of combustion are ultimately passed through a large pipe 232through an obnoxious vapor condenser 234 through a liquid condenser 236,blower 236 and stack 240. At suitable stages along the length of thetunnellike conduit I provide pipes 242, 244, 246 and 243 from which aportion of the gases of combustion are drawn and pass through separators266, thence through fans 252, pipes 254 from which point the products ofcombustion are forced in the manner hereinbefore described through thedrier compartment and then through the porous sludge supporting bed andthence through the sludge from which point the escaping gases ofcombustion and water vapor join with the products of combustion and arepassed through the pipe 232 to the stack as hereinbefore described. InFigs. 5. and 6 the course of the fluid sludge is indicated as passingfrom pipe 256 through the preliminary sludge warmer 258, thence to thebottom part of the sludge concentrator and evaporator 260, thence into asludge reservoir 262 from which point the sludge may be by-passed backthrough the concentrator or is passed into the float-controlled sludgefeed box 264 for automatic feeding onto the continuous drier.

With respect to that part of my invention wherein I propose to drysludge by subjecting it in a relatively finely divided condition to theaction of heated aeriform fluid, I may accomplish this in a-numberof'ways, depending upon the type of sludge to be handled. In certaininstances where liquid or fluid sludge is to be dried, I may project theliquid sludge in spray form in a manner to let it fall by gravity forsome distance through highly heated aeriform fluid such as heated air,heated combustible gases, or both, so that at the termination of thefall of the sprayed sludge, it will be combustibly preferto indry. Inother .i'eotbysprayingunderpressuremrtocentrifuge the either inliquid orsubstantially Oinchescfmercury.

stance the liquid sludge when thus spr'ayed'or injected in finelydivided conditionand particrendering the fluid sludge more porous, lesspasty, or non-cohesive. This material may be added to the sewage in thesedimentation tank II. The ingredient added need not necessarily becombustible, and/or I also propose to add a combustible, orheat-contributing ingredient to the fluid sludge, such, for instance, asa fuel so that after the sludge has been dried, and during itssubsequent burning in the furnace, this added fuel ingredient togetherwith the combustible sludge will provide sufficient heat for utilizationin drying additional quantities of sludge. In this last instance, thefuel which is to be added to the fluid sludge can be in any desired formsuch as flne coke, bituminous coal, wood shavings, or sawdust, or driedvegetable matter of any form.

Having thus described my invention, what I desire to secure by LettersPatent is as follows:

1. The herein-described process of reducing liquid sewage containingapproximately 96% water to combustible dryness for its sanitarydisposition by burning, comprising evaporating substantially from 50 to80% of the moisture content of sewage to provide a partly de-wateredfluid sludge, forming a layer of such substantially fluid sludge, andprojecting heated gas through said sludge layer to reduce the same tocombustible dryness, burning the dried sludge, and utilizing the heat ofthe products of combustion for drying additional quantities of thesewage.

2. The process of disposing of sewage comprising preliminarily removinga portion of the wa ter, the grit and coarse foreignmatter from the rawliquid sewage, settling and recovering the sludge from the sewage,preliminarily evaporating a substantial portion of the moisture of thefluid sludge, and thereafterheating the sludge to combustible dryness,burning the dried sludge with added fuel and utilizing the heat of theproducts of combustion in the drying and evaporation operations offurther sludge.

3. An apparatus of the character described, the

combination of a furnace, an evaporator, an air heater and a sludgedrier, means for passing the products ofcombustion from said furnace tosaid evaporator and then through said heater, and

meansforairthrough saidheatertoheattionofafurnscaanevaporatonaheatexehanger.

andasludgedrienmeansforpassingtheproducts of combustion from saidfurnace to the. evaporator, means for passing fluid sludge through theheat exchanger, through the evaporator and-into the drier, means forreducing the sludge to combustible dryness within the drier, and meansfor passingthesteamdischargedfromtheevapora-.

tor through the heat exchanger.

5. In a device of the class described, the combination of a furnace, aflrst heat exchanger, a second heat exchanger and a drier, means forpassingthegasesof combustionfromsaidfurnace to said second heatexchanger, means for aeriform fluid to said flrst heat exchanger, thento said second heat exchanger and for proiectng said heated air into thedrier and into contact with the sludge therein to reduce the same tocombustible dryness, and means for conveying the heated aerii'orm fluiddischarged from said drier to said flrst heat exchanger to heat the airpassing therethrough.

6. An apparatus of the character described comprising a furnace, asludge drier, a preliminary heater for the fluid sludge, an evaporatorfor the fluid sludge, means for projecting aeriform fluid through thesludge in the drier to reduce the same to combustible dryness, means forutilizing the heat of the products of combustion of the furnace forevaporating sludge in the evaporator and for thereafter heating theaeriform fluid, means for utilizing the steam in the evaporator forheating the preliminary sludge heater, and means for uti-' lizing thedischarged aeriform fluid from the drier for preliminarily heating theaeriform fluid.

7. An apparatus of the character described comprising a furnace, anevaporator, a heater, and an obnoxious vapor condenser and a sludgedrier, means for passing sewage sludge through the evaporator and thenceto the drier, means for heating the sludge in the drier to combustibledryness including connections for delivering heated gases from theheater to the drier, means for discharging the steam and vapor productsfrom the drier through the heater in order to heat the gases deliveredthence to the drier and means for discharging the steam and'vapor fromthe heater through the obnoxious vapor condenser, and

. means to deliver sludge from the drier to the furnace for ultimatesanitary destruction by burning.

8. In a device of the class described, the combination of a furnacehaving a relatively long extension containing an evaporator and alongitudinally extending drier, means for supporting a bed of sludge onsaid drier, a heat exchanger having a-wall forming a part of saidextension, means for passing hot gases of combustion from the furnacethrough the evaporator and the longitudinal extension and into contactwith the wall of the heat exchanger, means for passing the products oicombustion from the drier through the heat exchanger, means for passingair through the heat exchanger and into contact with said wall and forpassing the air thence through the sludge bed supported on the drier.

. JOSEPH HARRINGTON.

